1. Field of the Invention
This invention relates to electrophoresis cells for slab gel electrophoresis.
2. Description of the Related Art
Electrophoresis in vertically oriented slab gels is a process that is widely used for separating mixtures of chemical and biological species, such as proteins, oligopeptides, polypeptides, nucleic acids, and oligonucleotides. Among the numerous advantages of using slab gels are the ability to perform analyses on multiple samples at the same time, the ease of loading samples by inserting them in wells formed along the top edge of the slab, and the ease of placing the top and bottom edges of the slab in contact with separate buffer solutions for connection with separate electrodes.
In most applications, the slab is most conveniently cast in a sandwich-type arrangement between two flat transparent plates which are often combined in a unit that is referred to as a parallel plate gel enclosure or cassette. In use, the cassette is mounted in an electrophoresis cell, which provides electrical contact between the exposed edges of the gel and each of two electrodes through buffer solutions that carry the electric current between the electrodes and through the gel. The cell must contain the two buffer solutions and keep them separate from each other while maintaining full liquid contact between each buffer solution and the top and bottom edges of the gel, respectfully, and yet permit the user to insert and remove the cassette for analysis. Various cell designs have been developed that enable the user to assemble and disassemble the cell quickly so that successive runs can be performed in a routine manner, and when assembling the cell to do so securely, which is of value since improper assembly can result in leakage and failed experiments and the result may be lost time and sometimes lost samples as well. One such cell design is disclosed in U.S. Pat. No. 5,632,877, entitled xe2x80x9cRapid Assembly Electrophoresis Cell for Slab Gels,xe2x80x9d inventor D. van Atta, issued May 27, 1997.
The present invention resides in a pair of clamps designed to secure a cassette or parallel plate gel enclosures in general to a frame in a manner that will form the cassette and frame into buffer chambers as part of an electrophoresis cell. One of the various objects of this invention is to provide clamps that serve this purpose and yet are compact in design and structure, with dimensions not much larger than those of the cassette itself. Another object is to provide clamps that are readily secured and released and that when secured will provide a leak-free assembly.
These and other objects are achieved by a clamp construction that includes a support plate supporting two grasping members in the form of panels, preferably parallel, extending from one side of the support plate, each grasping member extending substantially the full length of a lateral edge of the cassette. A gap separates the two grasping members, the gap being sufficiently large to receive the lateral edge of the cassette and the frame in a snug fit. The grasping members themselves are substantially rigid, and any flexibility is sufficiently resilient that they compress the cassette against the frame with enough pressure to provide a liquid-tight seal. In the case where the frame is designed for two cassettes, one on either side. the gap between the grasping members is sufficiently larger to receive both cassettes and frame. When one or more gaskets are used to provide liquid-tight contact between the cassette(s) and the frame, the gap between the grasping members is large enough to receive the cassette(s), the frame and the gasket(s), all in a snug fit. To facilitate the placement of the clamp over these components, the leading edges of the inner faces of the grasping members are beveled. The clamp can thus be slipped over the cassettes and frame and provide an immediate clamping effect. The clamp serves all these purposes while leaving the upper and lower edges of the cassette exposed for contact with the electrode buffer solutions.
Certain additional features are included in preferred embodiments of the invention. One of these is a pivotal mounting of each clamp to the frame so that each clamp can be rotated into and out of the clamping position in which the clamp engages the cassette. Another is a protrusion extending from either or both of the lateral faces of the clamp, the protrusion(s) operating in conjunction with the pivotal mounting to produce a cam effect to enhance the sealing of the cassette against the frame.
This invention also resides in an assembly that includes a frame, one or two cassettes, a pair of clamps as described above, and optionally one or two gaskets. These and other features, embodiments, objects, and advantages of the invention will be better understood from the description that follows.